Travelers who want to infuse their trips with service to others may be outnumbered by sun-seekers lounging on the beach, but the trend of volunteer vacations is spreading fast.

Among college students, the alternative spring-break movement dates back more than a decade, and it's caught hold with a generation raised on service-learning. Break Away, a nonprofit that trains students to lead trips, estimates that nearly 40,000 college students a year now spend vacation time volunteering. But people of all ages are increasingly interested in making a difference in a world where the daily news brings word of orphans in Africa and hurricane survivors in the American South.

"People are seeing all these natural disasters around the world ... and they want to jump in and help out a little bit, as well as enjoy their vacation at the same time," says Amy Kaplan, a spokeswoman for i-to-i, a British company with offices in the United States that coordinates volunteer trips in 30 countries for about 5,000 people a year.

Global Volunteers, a nonprofit in St. Paul, Minn., started offering trips 23 years ago, several years after founders Bud Philbrook and Michele Gran spent part of their honeymoon volunteering in Guatemala. About 2,000 people a year sign up for their one- to three-week trips. The number has been growing about 20 percent a year, with the biggest uptick among those under age 30, says spokeswoman Barb DeGroot. For young adults, the most popular destinations are Costa Rica, Ghana, and Tanzania.

African countries are popular choices for i-to-i volunteers as well. One project in South Africa that fills up fast involves animal conservation work with lion cubs. Volunteers play with the cubs and bottle feed them. They also tackle less glamorous tasks such as cleaning. For beachgoers, there's a trip in South Africa where people learn to surf and then teach that skill to children who otherwise wouldn't have the opportunity.

The other countries in i-to-i's top five: India – particularly Bangalore, where people can work on community development, music, and film projects; Ecuador, which includes conservation trips to the Galápagos Islands; Costa Rica; and Sri Lanka.

Most volunteers serve three to four weeks, but i-to-i arranges longer and shorter ventures as well. On March 8, dozens of i-to-i volunteers are celebrating International Women's Day by working with women on health issues and life skills in Tanzania.

In addition to Africa, more volunteers are now interested in traveling to places like the Middle East as news coverage of the region increases, says David Santulli, executive director of United Planet, a volunteer organization in Boston. United Planet is starting to coordinate trips to such countries as Turkey, Jordan, and Morocco, and may also expand to Oman, Bahrain, and the United Arab Emirates.

Two-to-three-week trips are the most popular, Mr. Santulli says, but more volunteers have begun showing interest in staying abroad for six months or even a year.

If, on the other hand, you want to volunteer but also want to experience some typical tourist sights, i-to-i offers "meaningful tours." Take a trip to the Great Wall of China, for instance, and along the way give some love and attention to children at an orphanage or help out with Giant Panda conservation work.

Among college students, most campuses affiliated with Break Away are still organizing some trips to assist people in New Orleans and other areas damaged by hurricane Katrina. Other service projects involve everything from elderly care and collecting oral histories in Atlanta to land-mine problems in Vietnam. Some new issues gaining a foothold with several campus groups are refugees and prison reform.

"As the alternative-break movement matures, the students are really interested in the service-learning dimension of it.... They want social issues that they feel are really relevant and complex," says Jill Piacitelli, director of Atlanta-based Break Away. The nonprofit was started in 1991 by alumni of Vanderbilt University in Nashville, Tenn., who as undergrads had started a club focused on alternative spring breaks.

Typically, students spend part of the academic year raising money and planning their trips. (The average trip involves 10 to 12 people at a cost of about $318 per person, because students generally find cheap housing through local hosts.) "That's part of the grass-roots feel of alternative breaks," Ms. Piacitelli says. "You're building a group dynamic as you scrounge up money and end up sleeping on floors and eating peanut-butter-and-jelly sandwiches and having the time of your life."

The giving goes both directions, as one Florida woman noted in a posting to the Global Volunteers website after a week-long trip to help build houses in Appalachia. She describes the process of building up trust with the local residents who worked on the project, people who have lived in the coal-mining area for generations: "This is what Global Volunteers is about – learning from other volunteers and the people of the host communities; teaching each other in subtle ways about who we are; and just being willing to serve the world in some simple way.... As the week progressed, I could see change in the people I had met and feel a change in myself.... In our team journal, there is an anonymous quote: 'Live your life so your children can tell their children you stood for something wonderful.' "